The disclosed embodiments relate to a medical device. Specifically, the disclosed embodiments relate to a guide wire used for insertion of a catheter into a body lumen such as a blood vessel or a urinary duct, and for insertion of an indwelling instrument into an aneurysm formed in a blood vessel.
The guide wire used for insertion of a catheter into a body lumen and for insertion of an indwelling instrument into an aneurysm generally includes a core shaft, a coil body covering a distal end portion of the core shaft, and a joint joining the core shaft and the coil body.
For example, Japanese Patent Application Laid-open No. 2010-214054 describes a guide wire including a core wire (corresponding to a core shaft) formed of stainless steel, a coil spring (corresponding to a coil body) covering a distal end of the core wire, and a Au—Sn based solder (corresponding to a joint) joining the distal end of the core wire and a distal end of the coil spring (see FIG. 1, etc.). Japanese Patent Application Laid-open No. 2010-214054 also describes that Ag—Sn based solder is conventionally used instead of Au—Sn based solder to join the core wire and the coil spring ((see paragraph [0004], etc.). That is, Japanese Patent Application Laid-open No. 2010-214054 describes that either Ag—Sn based solder (hereinafter referred to as “silver-tin based solder”) or Au—Sn based solder (hereinafter referred to as “gold-tin based solder”) can be used to join a core shaft formed of stainless steel in the conventional guide wire.
However, the silver-tin based solder and the gold-tin based solder are different in joining strength depending on a material to be joined, and there has been a problem that especially for tungsten, sufficient joining strength cannot be secured for use as a guide wire, as described later.
Moreover, in the guide wire, the joining strength between the core shaft and the coil body is a considerably important element for the performance of the guide wire. For example, when the joining strength between the core shaft and the coil body is insufficient, there is a risk that the core shaft and the coil body will become separated from each other during procedures, and in the worst case, a distal end of the guide wire might remain in a patient's body.